1. Field of the Invention
This invention relates to hydraulic turbines having runners with generally horizontal axes of rotation. Particularly, this invention relates to a vibration-dampened discharge ring surrounding the runner to reduce noise and vibration emanating from the ring during operation of the turbine.
2. Description of the Prior Art
In the prior art, hydraulic turbines are well known for the production of hydroelectric power. Such turbines typically are constructed with cylindrical discharge rings surrounding the turbine blades for guiding flowing water past the blades.
Such turbines are constructed for either vertical or horizontal operation. In vertical turbines, the discharge ring is commonly embedded in a concrete foundation. Examples of such vertical turbines are found in U.S. Pat. Nos. 1,833,146 to Woodard dated Nov. 24, 1931; 1,934,636 to Martin dated Nov. 7, 1933 and 2,701,313 to Obrist dated Feb. 1, 1955. On horizontal turbines, the discharge ring is commonly exposed within an access chamber formed within the foundation such as shown in U.S. Pat. No. 3,535,540 to Boulogne dated Oct. 20, 1970.
Exposing the discharge ring to the atmosphere, as is common in horizontal turbines, has resulted in undesirable effects. Namely, vibrational forces caused by flowing water and operation of the turbine are transmitted to the discharge ring resulting in a great deal of noise emanating from the discharge ring. This noise is particularly troublesome when the turbines are installed near populous areas and to workers in the turbine powerhouse.
To deaden the noise, it has been suggested to coat the discharge ring with styrofoam or other insulating material. However, such attempts are only moderately successful since they fail to dampen the vibration which is the major source of the noise.
It is well known to dampen the vibration, and hence the noise, of an object by increasing its mass. However, such a suggestion applied to hydraulic turbines presents additional problems. Adding to the thickness of a discharge ring would increase its mass but such rings are formed from structural steel which is expensive and costly to shape.
Additionally, adding to the thickness of the discharge ring or permanently filling the discharge ring with a massive material greatly adds to the weight of the ring. At the time of installation of the ring, and at times during the life of the turbine, removal of the ring is necessary. By increasing the mass of the ring, the weight is so great that removal is impossible or requires very costly, heavy cranes and other equipment as well as costly modifications to foundations to support the equipment.
The object of the present invention is to provide a discharge ring of sufficient mass to eliminate the vibration of the ring and resulting noises.
It is a further object of the invention to provide a massive discharge ring which is susceptible to easy removal.